This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. This project is concerned with an antibody called 14F7, which recognizes the ganglioside N-glycolyl GM3. This molecule is very common in animal cells, but not found in human cells except on certain tumors. It is hence an ideal tumor marker. Previous studies of the Krengel group have characterized the crystal structure of the 14F7 Fab and predicted the antigen complex by computer modeling. The aim of this project is to provide experimental data to further characterize the antibody-antigen complex. We will employ oxidative footprinting to generate experimental data that may be used to compare the theoretical structure of the antibody-antigen complex. The project will start with production and purification of 14F7 Fab fragment from purified mAbs. This part of the project will take place at the Department of Chemistry in Oslo. The 14F7 Fab will then be trypsinized and the tryptic peptides characterized by mass spectrometry in collaboration with Dr. Wolfgang Egge-Jacobsen at the Department of Molecular Biosciences. Once these preparations are completed, the work will be continued at the University of Georgia.